Horsepower Converter

Horsepower comes in two flavors that differ by about 1.4%: mechanical horsepower (hp), used in the US and UK, and metric horsepower (PS or CV), used in Germany, Japan, and most of continental Europe. Both measure the same thing — engine output power — but with slightly different unit definitions.

The formula

1 mechanical hp (SAE) = 550 ft·lbf/s = 745.6999 W = 0.7457 kW
1 metric hp (PS/CV)   = 75 kgf·m/s  = 735.4988 W = 0.7355 kW

hp  → kW:  multiply by 0.7456999
PS  → kW:  multiply by 0.73549875   (75 × 9.80665 / 1000)
kW  → hp:  multiply by 1.3410221   (1 / 0.7456999)
kW  → PS:  multiply by 1.3596216   (1 / 0.73549875)

Source: NIST SP 811.

Practical examples

Example 1 — European car rated 200 PS. Convert to kW: 200 × 0.73550 = 147.1 kW. Convert to hp: 200 × 0.73550 / 0.74570 = 197.3 hp. (A 200 PS car is about 197 hp.)

Example 2 — US car rated 300 hp. Convert to kW: 300 × 0.74570 = 223.7 kW. In PS: 300 × 0.74570 / 0.73550 = 304.2 PS.

Example 3 — Electric vehicle rated 150 kW. In hp: 150 / 0.74570 = 201.2 hp. In PS: 150 / 0.73550 = 203.9 PS.

Common mistakes

• Treating hp and PS as identical. They differ by ~1.4%. A 200 PS car is about 197 hp, not 200 hp. For marketing comparisons this matters.
• Confusing gross and net horsepower. Older SAE gross ratings (1960s–early 1970s US muscle cars) measured without accessories; SAE net measures with all accessories installed. Modern ratings are SAE net. A 1970 engine rated "360 hp gross" might be ~290 hp net.
• Confusing rated power with peak power. Electric motors can sustain rated power indefinitely; internal combustion engine power ratings represent peak output at a specific RPM, not sustained output.

International and regional variations

Quick reference